Ball joint



FIG. 1 is a perspective view of my new design;

FIG. 2 is another perspective view thereof;

FIG. 3 is a side elevational view thereof, the opposite side being a mirror image;

FIG. 4 is another side elevational view thereof, the opposite side being a mirror image;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof.

The broken lines showing of FIGS. 1-6 are for illustrative purposes only and therefore establish no part of the claimed design. 

The ornamental design for a ball joint, as shown and described. 